2 weeks ago I had sex with my husband and within a few days...

I started having severe pain in my abdominal area and sides. It's also been in my back and I've been nauseous... had hemorrhoids ( I think). My doctor says it came back negative as an uti ... I have another appointment tomorrow... when we had sex, my husband came inside me. I've never felt or experienced this before. Does this sound like an STI/STD of some sort?